This project will investigate dietary and other lifestyle risk factors for cancer. Specifically, it will: 1) establish a large, multiethnic cohort (including several minority groups much in need of study) which will allow us to test a variety of hypotheses related to dietary and other risk factors; and 2) follow the cohort for incidence of cancer, as well as other chronic diseases. A substantial amount of work has already been accomplished towards these goals. A self-administered questionnaire, with a major dietary component, has been developed and pre-tested. In addition, a pilot study that entailed mailouts to 6,000 randomly selected individuals (representing the 4 ethnic groups included in this proposal) yielded an overall response rate of 52.3%, demonstrating the feasibility of the project. The study will consist of questionnaire mailings over a 2-year period to men and women aged 45-79, randomly selected from the four ethnic groups (blacks, Hispanics, Japanese, and Nonhispanic whites), in order to obtain a total cohort of 327,020 sons. In addition to a Quantitative diet history, the questionnaire will include background information as well as medical, medication, physical activity, and female reproductive histories. Drivers' license files will provide the sampling frame, and, based on the results of the pilot, will yield a participant group with notable differences in the food sources of particular nutrients among ethnic groups and a wide range of nutrient intakes within each group. Surveillance will begin in the third year, utilizing computer linkages with the population-based Hawaii and California statewide tumor registries, and direct contact with the subjects. After 4-5 years of follow-up on the cohort, the number of incident cases for several cancer sites will be adequate to address in the data analysis the major dietary hypotheses. Strengths of this project include its prospective design, large size, ethnic diversity, minority component, selection of subjects from the general population, variation in food sources and range of intake of nutrients, and the developmental work already completed. The findings should contribute significantly to the future primary prevention of cancer.